This application relates to and claims priority to corresponding German Patent Application No. 100 30 004.9 filed on Jun. 17, 2000, and corresponding European Patent Application No. 01113149.7 filed on May 30, 2001.
The invention relates to a device for mounting an optical element, for example a lens element in a lens, especially in an exposure lens in micro lithography.
Optical elements, especially lens elements, are generally mounted in what is known as a directional adhesive bonding mounting or inner mounting, which in turn is connected to an outer mounting. Mechanical distorting stresses may be applied to the optical element by the directional adhesive bonding mounting which impair the imaging accuracy of the optical element. In lenses for micro lithography, what are known as corrective elements, for example lens elements, are known which are designed for replacement in a lens in order to correct or eliminate residual optical errors.
In a replacement of an optical element, for example of a corrective lens, and subsequent reinstallation or installation of a different optical element, new errors, especially installation errors, may creep in.
Furthermore, it is often necessary to align optical elements, in particular lens elements, which are situated at a directional adhesive bonding point for installation, with their optical axes at right angles to the mounting of the lens.
It is therefore an object of the present invention to provide a device of the type mentioned initially which applies no distorting stresses to the optical element and which also ensures that, when the optical element is replaced and reinstallation takes place, no new errors Iran arise or a reproducible reinstallation is achieved.
It is a further object of the invention at the same time to provide for tilting adjustment or precise setting adjustment of the optical element during installation or following removal and refitting.
This object is achieved, according to the invention, by the features mentioned in claim 1.
According to the invention, the optical element now simultaneously takes on the function of an inner mounting or the latter is integrated into the optical element. To this end, it is merely necessary to provide a corresponding edge zone with support points, for which purpose it a generally merely necessary to enlarge the diameter of the optical element slightly.
As a result of the precise assignment of the support points and the counterbearing points, not only is reproducibility during installation and removal achieved but, an addition, there are also no mechanical distorting stresses because of the absence of directional adhesive bonding points.
In an advantageous embodiment of the invention, provision may be made for the edge zone of the optical element with the support points to form at least approximately a flat surface, whereby good reproducibility can be achieved.
In a very advantageous embodiment of the invention, provision may be made for the support points, the counterbearing points and the bearing members to form a three-point bearing with a planar support, a groove-shaped support and a fixed-point support.
In a very advantageous embodiment of the invention, provision may be made, in order to set a tilting adjustment during installation for the support points, which are formed, for example, by V-shaped channels or grooves, to lie at an angle with respect to a plane which lies at right angles to the z axis. This is generally the horizontal plane. In addition to providing improved centering of the optical element, this embodiment makes it possible, by simple lateral displacement of the support points (one or more) in the radial direction, to change the height of the optical element at this point, with the result that, on account of a change in height of the bearing points on the optical element, the latter is tilted The resolution can be set by selecting the angle of inclination, with the result that the tilting can be corrected for down to very low values.
The above adjustment method, if necessary, can be employed even during installation, without any dismantling of the support feet being required. In this way, a corresponding amount of time is saved.
In another embodiment, it is possible to provide for the bearing points to be formed by V-shaped grooves or channels, with the longitudinal walls of the grooves or channels at an angle to one another.
Normally, the channel walls run parallel to one another. If, according to the invention, these walls are now arranged at an angle to one another, it is possible, by radial displacement of a supper point, once again to effect tilting of the optical element. As a result of a corresponding displacement, the penetration depth of the bearing bodies changes and therefore so does the z height of the support point.
If, in an alternative solution, the counterbearing points at which the bearing bodies are arranged lie at an angle to a plane which is at right angles to the z axis, in general at an angle to the horizontal plane, a radial displacement of the support points on the inclined mounting also changes the height position of the support point of the bearing body on the optical element accordingly. In this way, tilting is once again generated. The resolution can then be set by means of the angle. Naturally, the same angle has then to be provided on the outer mounting.